Rhodamine B adsorption by activated carbon: Kinetic and equilibrium studies

A carbonaceous adsorbent (TPC) prepared from Thespusia populinia bark by acid treatment was tested for its efficiency in removing Rhodamine B (RDB). The parameters studied include agitation time, initial dye concentration, carbon dose, pH and temperature. The adsorption followed first order reaction equation and the rate is mainly controlled by intra-particle diffusion. Freundlich and Langmuir isotherm models were applied to the equilibrium data. The adsorption capacity (Qm) obtained from the Langmuir isotherm plots were 60.836, 64.239, 68.695 and 77.178 mg/g respectively at an initial pH of 7.0 at 30, 40, 50 and 60C. The temperature variation study showed that the RDB adsorption is endothermic and spontaneous with increased randomness at the solid solution interface. Significant effect on adsorption was observed on varying the pH of the RDB solutions. Almost 79% removal of RDB was observed at 60C. The Langmuir and Freundlich isotherms obtained, positive H value, pH dependent results and desorption of dye in mineral acid suggest that the adsorption of RDB on TPC involves physisorption mechanism.